1. Field of the Invention
The invention relates to a lens module having a positioning structure, and more particularly to the lens module that applies a compensation module to reduce a Z-axis tilt to an allowable extent so as to ensue the image-capturing quality, in which the Z-axis tilt is generated from improper engagement between the optical lens module and the image sensor module.
2. Description of the Prior Art
Referring to FIG. 1, an exploded view of a conventional focusing 0r zooming lens set is shown, in which a mechanical focusing mechanism 7 is used. The mechanical focusing drive unit 7 applies an expensive precision drive unit 71 to drive the carrier 73 carrying the lens set 72, in which the precision drive unit 71 is one of a step motor, a supersonic motor, a piezoelectric actuator and the like. For the drive unit 71 is consisted of plenty transmission members, the mechanism thereof is complicated, needs much work to assembly, occupies a larger room, costs higher, and consumes more electricity. All of these reasons contribute to the high and hard-to-be-reduced price of the lens set.
In the art, the photographing is cumbersome in human light-detecting, hand focusing or zooming, hand reeling, and the like. The consequence of involving too much human work or too many human reasons in photographing is an inevitable mistake somewhere and sometime. Obviously, it is kind of tragedy to have mistakes in scene taking, for the timing thereof is once and no more. Namely, in the art, the quality of the photographing is highly dependent of the training of the photographers. As the development in mechanical automations during 50's and 60's, the auto light-detector and the auto film-reeler are firstly seen in the photographing techniques. Such an improvement initiates a complete automation in the field of photographing. Among all the changes, a key and the most popular technique for the photography automation is the auto-focusing system, which ensures the photo-taking rate.
It is now already the trend to replace the conventional professional photographing gears by the modern photographing set featured in better resolutions, lighter weight, slimmer and shorter body. However, even all the progresses and advantages in automation, the mechanical motor such as the step motor is still applied but causes problems in irreducible body occupation and thus in further minimizing the product.
On the other hand, another progress in the photography technology is the invention of the voice coil motor (VCM), which adapts modern electromagnetic technique to load a feedback control system for monitoring the deviation of the coil assembly and so as able to replace the step motor and to further reduce the poor precision problems caused by mechanical backlashes and production tolerances. In addition, another trend in the photography technology is to integrate various fancy functions into a unique product, such as the mobile phone with both photographing and communication functions, the PDA with built-in camera, and the notebook computer capable of videotaping.
Nevertheless, for most of the lens modules in the marketplace, the optical lens module is mounted along a Z-axis on an image sensor module located on an X-Y plane, such that the image sensor module can apply the optical lens module to capture foreign images. Also, most of the lens modules do not build in an anti-tilt mechanism, in which the tilt is particularly the Z-axis tilt between the image capturing axis of the optical lens module and the image capturing path of the image sensor module. Namely, the existing manufacturing Z-axis tilt upon the lens module can be resolved. In assembling the lens module, possible smoothness problems on the contact surfaces may lead to the tilt of the image capturing axis with respect to the image capturing path of the image sensor module. Further, such a tilt would affect negatively the linearity, repeatability, straightness, and perpendicularity of the lens set with respect to the optical axis. Apparently, the manufacturing tilt in the image capturing axis would have lost control of each of the lens modules in Z-axis tilt after the production. As a consequence, the overall imaging quality of the lens module as well as the position precision for the displaceable lens set would be reduced to some extent.